For Ben Affleck, having a son meant he could impart some special fatherly wisdom at last.

His wife, Jennifer Garner, stopped by the Tonight Show to promote her new movie Draft Day and talk about their kids: Violet, 8, Seraphina, 5, and Samuel, 2. But things got a little more than G-rated when discussing what Affleck, 41, has taught his youngest child.

“He’s so psyched to finally have a boy. He loves his girls, but he’s serious about his son right now,” Garner, 41, told Jimmy Fallon on Wednesday’s episode.

“So he taught him about his bits. He taught him about his P and two N’s.”

As it turns out, the newest Batman is all about teaching biology.

“Now every time we pass a dog who’s walking on the street, or if we’re at a zoo or something, our poor little son is crouching down, looking up, and he’s like, ‘Mama, does that have a vagina or a penis and two nuts?’” Garner explained, laughing. “That’s what Ben has been up to.”